The other kinds of articles that may be familiar to you include newspaper articles and magazine articles. While these kinds of resources can be appropriate for some kinds of research, a journal article is what is required for academic citation and writing. What's the difference?
Journal articles usually go through a formal review process, often called peer-review or scholarly review before accepted for publication. This means the journal's editor sends copies of the submitted article to experts on the article's topic, but without any indication of the author's identity. The expert may or may not know the author, so having the author's name removes a possible source of bias. This is the scholarly version of the blind audition.
How do you know a journal uses this process? Look at the editorial guidelines or the information for authors for that journal. Many of the articles cited in Grove Music bibliographies or in other scholarly writings will be published in peer-reviewed journals. WARNING! While some library databases (such as Academic Search Complete) have a checkbox for Scholarly (Peer Reviewed) Journals, those results are not always accurate.
Examples of peer-reviewed journals include, but are not limited to:
My favorite two methods for finding article citations:
Once you've located citations, you can use the Online Journals A-Z list to see if the journal is available at FSU in online full-text or in printed form. If the journal is not available at FSU, you can request a copy of the journal article using Interlibrary Loan (ILL). Many of the online resources, such as RILM, Music Index, or Academic Search Complete have by entries to make locating (or requesting through ILL) the actual article easier.